Method and device to evaporate active ingredients from a liquid solution

ABSTRACT

A method to evaporate active ingredients from a liquid solution, in which said liquid solution includes a solvent and at least one type of active ingredient, the method including dispensing in controlled time periods doses of said liquid solution on a liquid retaining support, where the solvent is evaporated from the support such that only the active ingredient remains on the support, and where the active ingredient is evaporated from the support after most of the solvent has evaporated.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/526,960 filed on 13 Aug. 2009, which is the U.S. National Phase ofInternational Patent Application Number PCT/EP2008/051627 filed on 11Feb. 2008, which claims priority to Spanish Patent Application NumberP200700384 filed on 13 Feb. 2007, where the entire contents of all ofsaid applications are herein incorporated by reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method and a device to evaporate lowvolatility active substances or ingredients from a liquid solution. Theinvention is preferably used to evaporate an insecticide substance atlow temperature or even at room temperature.

More specifically, the invention includes distributing in the air activeingredients in a controlled manner to control the efficacy of the effectof the active ingredient considering the effective time of evaporationof the liquid, such that the beneficial effects of the activeingredients can be offered to the user as long as possible.

The field of application of the present invention is the industrialsector dedicated to the devices that evaporate volatile products such asperfumes, deodorants, odor and smoke neutralizes, bactericides, insectrepellents and air fresheners for interiors in general.

BRIEF DESCRIPTION OF RELATED ART

In dispensing volatile substances to perfume or purify the air of aroom, there are many situations in which it is desirable and evennecessary to supply one or more doses of product during a more or fesslong time interval, in order to then stop diffusing the product untilanother later time. This is the case, for example, of air fresheners forbathrooms, where it is desirable to release a small dose for a fewinstants and in which no more product is consumed until the user needsit again inside the bathroom. The same happens with insecticides, whichare also used during certain times of the day but not continuously, andthey are not needed for the rest of the time.

Multiple devices are currently known which manually or automaticallyallow diffusing the desired active ingredients of a liquid compound bymeans of a timer, spraying the liquid in an individual dose only atcertain instants chosen by the user because the user actuates the sprayhimself or herself or without any assistance from the user, havingpreviously programmed the timer periodically activating the spraying ofthe product.

However, these aerosol devices may not be completely effective orinexpensive because the effects of the active ingredients areconcentrated in the instant in which the spraying starts and thendecrease rapidly. It is therefore convenient for the liquid not to bedirectly distributed to the air but to a retaining element allowing agradual evaporation and therefore a more continuous supply of saidactive ingredients. To date, known evaporators incorporating anabsorbent element made of porous material containing the volatilesubstances are disposable devices having the drawback that said elementis impregnated in the factory during the process for manufacturing theproduct, such that the user receives the element impregnated only withthe active ingredients because the solvent spontaneously evaporatesbeforehand, part of the active ingredient possibly having evaporatedduring the product storage period. Once most of the active ingredienthas evaporated, the device loses its efficiency and must be replaced bya new one.

Several types of diffusers of low volatility active ingredients, such asinsecticides, are known, among which electrical devices which can beplugged into a socket can be mentioned; such devices are made up of abottle with a liquid solution formed by a solvent plus a smallpercentage of an active ingredient, as well as a wick partly housedinside the bottle allowing said liquid to rise to an upper part of thewick by capillarity means; the wick is subjected to a high temperatureto cause the evaporation of the solvent and of the active ingredient. Atemperature between 120 and 150° C. is generally required to achieve anunacceptable evaporation rate and suitable biological efficiency foreliminating flies and mosquitoes. This temperature range is much higherthan the temperature used in air freshener or perfuming devices usingthe same evaporation technique (approximately 70° C.) but is a must toevaporate the insecticide active ingredient. In addition, electricalportable devices are also known in which the volatile substance is insolid form, fixed upon a porous support. In the process formanufacturing said support, an amount of a liquid solution is metered onthe support such that said support is impregnated with said solutionformed by a solvent and the active ingredient. The solvent subsequentlyevaporates such that when the support is marketed it is impregnated onlywith the active ingredient. In these devices, once the solvent hasevaporated, only the active ingredient in liquid or solid state remainson the support, such that the active ingredient is able to evaporate atlow temperature or even at room temperature. Due to low consumptionrequired, these types of device can be manufactured and marketed with abattery supply. The great drawback of these devices is that they by nomeans show the remaining amount of substance to be evaporated andtherefore the remaining duration and the time of protection againstmosquitoes for the user, in the case of an insecticide diffuser.

Some devices have attempted to solve this drawback, for example, thedevice disclosed in U.S. Pat. No. 6,484,438 in which a second reservoirwith a volatile product without activity has been added. However, thistype of solution is not reliable, because if the physical properties ofthe two substances have been adjusted so that they evaporate in the sametime period, this will happen only in certain environmental temperatureand humidity conditions which will have been considered normal whiledefining the product. In reality, the product can be used in differentplaces and in different seasons of the year, therefore the environmentalconditions can be substantially different from those defined as normal,which will involve a lag between the evaporation of the indicator liquidand of the active ingredient.

BRIEF SUMMARY OF THE INVENTION

The present invention solves the technical drawback set forth by meansof the inventive subject-matter comprised in the attached independentclaims.

One of the aspects of the invention includes of a three step evaporationmethod during the use of the device by the consumer or user. The methodcomprises the following phases:

1) metering of a liquid solution upon a liquid retaining support, inwhich said liquid solution comprises a solvent and at least one type ofactive ingredient,

2) evaporation of the solvent,

3) evaporation of the active ingredient, The invention takes intoaccount that as long as the solvent has not evaporated, the activeingredient is not able to evaporate without a high temperature input,which is incompatible with the implementation of a portablebattery-powered device The present invention thus considers step 2 asespecially relevant, therefore a complete evaporation of the solventfrom the support is assured before dispensing a new dose of liquidsolution.

The method object of the invention is based on the periodic metering ofa dose of liquid solution, either by means of impulse activation by theuser or by means of an automatic cyclic function in which activationmeans cause the dispensing of a dose. In any case, means are providedwhich prevent a new dose from being dispensed until most of the solventof the previous dose has evaporated.

Therefore, a first aspect of the invention relates to a method toevaporate active ingredients from a liquid solution, which comprisesdispensing in controlled time periods doses of said liquid solution upona liquid retaining support, such that first the solvent evaporates fromsaid support, only the active ingredient remaining on the support.Subsequently, in the absence of the solvent, the active ingredient isable to evaporate by itself, and therefore the active ingredientevaporates from the support after most of the solvent has evaporated.

The evaporation of the solvent and of the active ingredient can occurspontaneously or can be controlled to accelerate the process, forexample, by applying an air stream on the support and/or by applyingheat, either during the evaporation of the solvent to reduce theduration of phase 2 or also during phase 3. The solvent and/or theactive ingredient can be heated at low temperature during theirevaporation, for example at a temperature less than 100° C., less than70° C. or even at room temperature.

The time periods between doses are controlled in the method such thateach dose of the liquid solution is dispensed on said support at aninstant in time after the evaporation of most of the active ingredientof the previous dose from the support. A dose is thus prevented frombeing dispensed on the support when the active ingredient retainedtherein from the previous dose has still not evaporated,

The time periods between doses are controlled by means of a timerdevice, preferably an electronic timer which is associated withelectromechanical means to allow dispensing a dose of liquid solutionafter the established time period between doses. The time necessary toevaporate the solvent and the time of evaporation of the activeingredient are determined by the manufacturer according to thesubstances used and the evaporation conditions for each practicalimplementation of the invention, such that the electronic timer isprogrammed, or designed in the case of a mechanical timer, to beactivated in a time period similar to or greater than that necessary toevaporate most of the solvent and active ingredient. After this time,the timer activates electronic and/or mechanical means which enabledispensing a new dose of liquid solution. Therefore, during the timeperiod in which the timer is not activated, the liquid dispensing meansare blocked and cannot dispense doses.

After activating the timer and subsequently enabling the dispensingmeans, a dose of liquid solution can be dispensed by impulse activationby the user at the time when the user considers it necessary to dispensea new dose. Alternatively, a dose of liquid solution can be dispensedautomatically, for which purpose there are mechanical means controlledby an electronic circuit which act on the dispensing means after theestablished time period between doses. In another aspect, the inventionconsists of a device to evaporate active ingredients from a liquidsolution, having a casing with an opening allowing the passage of air,and a reservoir containing said liquid solution. The device comprises atleast one liquid retaining support and dispensing means arranged in thecasing at a distance and in a suitable position for dispensing doses ofsaid liquid solution on said support. The device further has a timeradapted to allow the operation of said dispensing means in selected timeperiods, said time periods being greater than the time necessary forevaporating most of the solvent and active ingredient from the support.

The timer device is programmed to a time period corresponding to thetime between the metering of two consecutive doses, said time periodbeing similar to the time necessary for evaporating the solvent and thenthe active ingredient from the support.

The invention mainly improves two critical points in the performance ofthe volatile product: on one hand, it prevents impregnating the porousmaterial with the liquid in the factory, such that the user can use theeffects of the in situ transfer of the liquid to the evaporator support,because all the active ingredient dispensed is used since nothing islost during the product storage time, or even in the manufacture fromwhen the liquid is dispensed until the product is packaged.

The device of the invention can be manufactured in a simple, inexpensivemanner in order to form a portable and easy to handle device, with thepossibility of being reused with the incorporation of refills of thereservoir of the liquid solution.

BRIEF DESCRIPTION OF THE DRAWINGS

To complement the description being made and with the aim of aiding tobetter understand the features of the invention according to a preferredpractical embodiment thereof, a set of drawings is attached as anintegral part of said description, in which the following is shown withan illustrative and non-limiting character:

FIG. 1 shows a representative graph of the duration times of the threephases of the evaporation method of the invention, corresponding to adispensed dose of liquid solution. The vertical y-axis indicates theamount of evaporated product and the horizontal x-axis corresponds totime.

FIG. 2 shows in FIG. 2( a) a perspective view of a preferred embodimentof the device of the invention without the upper half of the casing inorder to show the components housed inside and illustrate the connectionbetween the pushbutton and the spray. FIG. 2( b) shows a rear view ofthe device shown in FIG. 2( a).

DETAILED DESCRIPTION OF THE INVENTION

The method of the invention is based on the discontinuity of themetering, for which the metering can occur by a technique known in thestate of the art, for example by means of: dripping, by means of a sprayor aerosol, or by means of breaking capsules or microcapsules containingthe liquid solution. There are optionally evaporation means such as alow consumption heater, i.e. a low temperature heater, a fan or acombination of both elements. These evaporation means can workcontinuously or discontinuously, for example they can be activated atthe same time a dose is dispensed.

The device can be a known device provided with absorption means forabsorbing the liquid by capillarity, such as a wick for example, inwhich the capillary transport is slow enough to allow the interruptionof the feed of the liquid in the evaporation area when the evaporationmeans are activated, If the amount of evaporated solvent is notsubstituted by more solvent, the active ingredient present alone in thewick will evaporate.

FIG. 1 shows a three step or phase evaporation cycle. Phase 1,consisting of the metering of an amount of solution, occurs almostinstantaneously at instant t1. Phase 2 corresponds to a high evaporationrate of the solvent between instants t1 and t2 in a short time period,and finally phase 3 consists of a low evaporation rate of the activeingredient between instants t2 and t3. The next dose of liquid solutioncan only occur after instant t3.

In practice, evaporation processes logically do not occur uniformly onthe entire evaporation surface due to the different evaporationconditions, such that it is possible that while certain areas of theevaporation surface are in phase 2, other areas are in phase 3.

The duration of phase 2 has been especially designed so that it is asfast as possible, as until the solvent has evaporated, the activitycaused by the active ingredient is very low or nil and therefore theefficiency of the product is virtually nil. It can be considered thatphase 2 ends when most of the solvent has evaporated, i.e., when theamount of solvent present in most of the evaporation area is so smallthat the active ingredient is able to evaporate in an effective manner.In phase 3, the active ingredient present in the evaporation areawithout solvent evaporates, and the amount of this active ingredientdecreases until the evaporation rate is not enough to ensure thenecessary biological efficiency to kill insects, for example. Thetransition between phases naturally does not occur instantaneously, butrather it is a gradual process depending on the particular evaporationconditions, it can therefore be considered that the duration of phase 3starts with the beginning of the evaporation of the active ingredient inan effective amount and ends when the amount of this ingredient presentin the evaporation area is no longer enough to ensure biologicalefficiency.

The duration between the metering of two consecutive doses iscontrolled, such that a dose is not metered as long as phase 3 of theprevious dose has not ended. If the next dose is metered before phase 2of the previous dose ends, the active ingredient will virtually stillnot have evaporated. On the other hand, if the next dose is metered along time after phase 3 of the previous dose has ended, i.e. long afterthe active ingredient has evaporated, the efficiency of the device willbe nil for a long time period during which the user will have noprotection against mosquitoes, for example.

The invention has means for preventing the premature interruption ofphase 2, for example, in the event that the user, with the intention ofincreasing the efficiency, activates the device for a second time todispense another dose of the liquid. In such case, the effect would beopposite to that desired, i.e., the efficiency will be nil. Indeed, ifthe metering is activated again during the duration of phase 2, theactive ingredient will never be alone and is therefore not able toevaporate. Furthermore, the new phase 2 will be longer than thatdetermined, because more amount of solvent will have to be evaporated,the amount of solvent already existing from the first metering and theamount of solvent provided with the second metering.

To prevent this situation, the invention incorporates means preventingpremature metering. By way of example, these means can be:

-   -   electronic means; an electronic timer disconnecting or blocking        the metering means for a minimum time period,    -   mechanical means: an activation button with a long period for        recovering the initial position once it has been pressed,

The present invention provides the shortest possible duration for phase2 because during phase 2 the efficiency of the device is virtually nil.The duration of phase 2 can be reduced using a high volatility solvent.According to the present invention, a high volatility solvent canconsist of a solvent or a mixture of solvents selected to obtain a vaporpressure at room temperature that is equal to or greater than 0.08 mmHg.

In another preferred embodiment, the duration of phase 2 can be reducedby increasing the concentration of active ingredient in the solution,because with less amount of solvent, less time is necessary to evaporateit. It has been found that an optimal composition can be obtained with 5to 70% w/w of active ingredient and preferably in a range comprisedbetween 20 to 65% w/w.

In another preferred embodiment, the duration of phase 2 is reduced byincreasing the evaporation area for the liquid, which can be obtainedfor example by means of:

-   -   metering of small liquid droplets,    -   metering upon a wide area of the liquid retaining support,    -   metering on a high roughness support, —arranging the support in        an inclined manner in relation to the metering direction of the        liquid, such that the excess liquid will flow down along the        surface    -   using a low surface tension solvent, such that the tendency to        form droplets decreases, which involves less surface per unit of        volume. In the present invention, a low surface tension solvent        must be understood as a solvent or a mixture of solvents        selected to achieve a surface tension at 25° C. that is equal to        or less than 26 mM/m. in another preferred embodiment, the        duration of phase 2 is reduced by reducing the absorption        capacity of the support, i.e. preventing the support material        from acting as a reservoir of the solvent and the latter being        more exposed. For example, in the present invention it has been        found that an optimal degree of porosity of the support for        obtaining the desired effect is obtained with a material with a        liquid absorption capacity of less than 1 g/cm³, preferably less        than 0.1 g/cm³.

In another preferred embodiment, the duration of phase 2 is reduced byusing a three phase emulsion. For example, said emulsion can be formedby a first solvent A compatible with the active ingredient that isdissolved in it, plus a solvent B in which the active ingredient is notsoluble. Both solvents can be mixed together. Some examples of suitablesolvents for solvent A are organic solvents such as isoparaffins,propylene glycol ethers, dearomatized hydrocarbons, naphthenichydrocarbons and acetone. Some examples for solvent B are: water, lowmolecular weight alcohols such as ethanol and methanol. The amount ofsolvent A is preferably less than 30% w/w.

In other examples conventional surfactants or surface-active agents canbe used, including anionic surfactants, ionic surfactants, amphotericsurfactants and any combination of the above.

In another preferred embodiment, the duration of phase 2 is reduced byusing a solvent in which the active ingredient is not soluble, such thatwhen the active ingredient in solid state is arranged in suspension inthe solvent, the solvent and active ingredient separation process isfaster. Some suitable solvents for this function are water, lowmolecular weight alcohols such as ethanol and methanol and any mixturethereof. Conventional surfactants, for example, can also be used,including anionic surfactants, ionic surfactants, amphoteric surfactantsand any combination of the above.

Nevertheless, despite reducing the duration of phase 2, this phase willcontinue to exist even though it is for a short time period, duringwhich virtually nil efficiency is obtained. In the case of practical,high-efficiency demanding applications, the existence of phase 2 wouldnot be acceptable, even if it had a very small duration.

For these types of applications, the invention provides a deviceprovided with at least two evaporation areas in which the doses ofliquid solution are dispensed in a coordinated manner in the twodifferent liquid retaining supports at different instants in time, suchthat the active ingredient without solvent is always available in atleast one of said supports, i.e. the three phase evaporation occurs inan alternating manner. In this device, the beginning of the cycle willcorrespond to the metering of the liquid on a first evaporation surface{phase 1) and the active ingredient will evaporate by itself from asecond evaporation surface {phase 3). Therefore, when the activeingredient is on the second evaporation surface (end of phase 3), phase2 on the first surface will have ended and this evaporation surface willbe ready for a new phase 3. In the case of an automatic and timedfunction, a new cycle will start by metering on the second surface andevaporating from the first surface.

FIG. 2 shows a practical embodiment of the invention, consisting of aportable device for diffusing active ingredients coming from a liquidsolution. The device is made up of a casing (1) formed in this case byan upper half and a lower half, which casing is provided with at feastone opening (11) for the passage of air, and a reservoir (2) containingsaid liquid solution comprising a solvent and at least one type ofactive ingredient. The device comprises at least one liquid retainingsupport (not shown) which can be manufactured from a material such as:paper, cardboard, cloth, unwoven cloth, ceramic, carbon fiber, orthermoplastic, and can adopt any shape considered to be suitable forfulfilling its functionality. FIG. 1 a shows a support structure (12) onwhich the retaining support in the form of fabric or paper, for example,is assembled.

The liquid retaining support can be made of a porous material having aliquid absorption capacity of less than 1 g/cm³, and preferably 0.1g/cm³, Alternatively, the retaining support can be made of a non-porousmaterial, such as a thermoplastic material for example, with thepossibility of being structured, i.e. having a rough surface or asurface provided with any type of raised design such as for examplelines or grooves preventing the liquid from falling to the floor when itis metered. The device further has dispensing means, consisting in thisembodiment of a conventional spray (14) assembled on the reservoir (2),similar to known cologne sprays. These dispensing means (14) arearranged in the casing (1) in a suitable position to dispense doses ofthe liquid solution on said support, in this case when the spray ispressed. Alternatively, the dispensing means are dripping means whichcan dispense droplets of the liquid solution, or the dispensing meanscan meter a dose of liquid solution by means of breaking capsules ormicrocapsules containing said liquid solution.

The casing (1) has an opening (16) from which the reservoir (2) can beseen from outside, which reservoir can be transparent or translucentsuch that the user can check the amount of liquid solution remaining inthe reservoir, so that the user can perceive when the liquid has run outand substitute the reservoir with a new one.

The liquid retaining support housed inside the casing is arrangedbetween the air outlet (11) and the dispensing means (15).

The device further comprises a fan (17) arranged in said casing in asuitable position to provide an air stream on said liquid retainingsupport, for the purpose of accelerating the evaporation of the solventand/or the active ingredient and propel it towards the outside throughthe outlet (11), The fan is formed by a small direct current motor (4)and an air propelling element (3), in this case in the form a squirrelcage, assembled on the motor shaft.

In another preferred embodiment, the device has conventional heatingmeans (not shown) arranged inside the casing in a suitable position toheat the components of the liquid solution retained by the support at alow temperature. The device includes a push-button (6) assembled in apivoting manner on a cylindrical shaft (18) fixed to the casing (1) suchthat a part of this push-button (6) can be accessed from the outside toallow its impulse activation by the user. At its inner part, thepush-button (6) has an arm (19) sized and located to press against thespray (14) as can be seen in FIG. 1 a, such that the spray expels a doseon the support when the user presses the push-button (6) towards theinside of the casing (1).

The device is provided with an electronic circuit (5) including anelectronic timer of a type known by a person skilled in the art. Thetimer is programmed to a time greater than the time necessary for theevaporation of the solvent and the subsequent evaporation of the activeingredient, which are known beforehand.

In addition, there is a swivel arm or rocker (7), consisting of an armassembled with the capacity to swivel on a shaft (15) integral with thecasing. The rocker (7) has a first end (8) suitably located close to thefree end of the arm (19), such that when the push-button (6) is pressedtowards the inside of the casing, said arm (19) moves this first end (8)of the rocker downwards, which rocker swivels such that the second end(9) thereof moves upwards. The second end (9) is positioned close to apush-button or switch (not shown) of the electronic circuit (5), suchthat when said second end (9) moves upwards, it presses said pushbutton,which starts the count of the timer. The free end of the arm (19) isshaped to make contact with the first end (8) of the rocker (7),preferably having a wedge shape which causes, when the pushbutton (6) ispressed, its end fitted inside the casing (1) to reach the contactsurface of the first end (8) of the rocker (7), translating the movementof the pushbutton (6) into a shift in reverse directions of each end (8,9) of said rocker (7). Alternatively, the actuation of said push-buttonalso starts the operation of the fan (17) and/or the heating means, aswell as a luminous indicator element, such as an LED for example actingas an element indicating to the user when the previous elements are onor off. The LED remains on during the memorized time for the timer, suchthat when this time ends, the LED also turns off to indicate to the userthat the effect of a dose has ended due to the evaporation of most ofthe active ingredient, and therefore the user can now start the processagain whenever he or she desires by pressing the push-button, activatingall the electric components simultaneously as explained below: i) He orshe presses the spray to release a single dose of liquid whichimmediately impregnates the retaining element, ii) He or she activatesthe electric circuit starting the operation of the fan to project airtowards the retaining element in order to favor the evaporation of theliquid absorbed by said retaining element and release the activeingredients into the air through an outlet provided in the casing. iii)At the same instant, the count of the timer of the electric circuit isrestarted, this timer being programmed in the factory taking intoaccount the time it takes for the liquid to evaporate completely and forall the concentration of active ingredients comprised in the defineddose to be diffused. iv) If signaling means are provided, at the sametime that the timer and the fan start working or when both finish, saidsignaling means are activated (for example, a luminous indicator turnson or an alarm ringing when the operating time of the timer and the fanturns off), notifying the user that if he or she wants the device tocontinue operating, he or she can restart the entire process again:spraying-evaporating-timing. Optionally, the process can beautomatically started by including actuation means for actuating thepush-button in the device itself or by remote control.

In a preferred embodiment, the device has means blocking the operationof the spray, said means being controlled by the timer, such that when adose of liquid is dispensed on the support, the count of the timerstarts and said blocking means are actuated, preventing the spray frombeing activated again while the timer is still counting. Since the timeris programmed to a time period that is similar to or greater than thetime necessary for evaporating most of the solvent and active ingredientfrom the support, the user is prevented from dispensing a new dose whilethere is still active ingredient in the support in a sufficient amountto be effective, because the spray is blocked during this time period.

Alternatively, the activation of the spray can be automatic, for whichpurpose the device has spray actuation means (not shown) causing saidactivation, which means are also controlled by the timer, such that whenthe timer finishes its time count, the spray is automatically activatedafter a pre-established time interval, which can be adjusted by theuser, for example, In relation said actuation means, for example, themotor (4) itself could be used to move the pushbutton (6) in a suitablemanner to press the spray (14).

The device is portable and powered by battery (13).

In a practical embodiment, the user can choose between a manual orautomatic operation, and within the automatic operation, he or she canselect various previously programmed metering time intervals accordingto his or her tastes or needs.

In another alternative embodiment of the invention, the device is notcontrolled by the timer and does not reproduce the three evaporationphases, i.e. it simply meters active ingredient, but incorporates allthe previously described elements; casing, support, dispenser,push-button, fan and heater.

The device can optionally have securing means to be fixed to the body ofa person or animal, such as for example a strap, a clip, etc.

Several possibilities of practical embodiments of the invention aredescribed in the attached dependent claims.

In view of this description and set of drawings, a person skilled in theart can understand that the embodiments of the invention which have beendescribed can be combined in many ways within the object of theinvention. The invention has been described according to severalpreferred embodiments thereof but it will be evident for a personskilled in the art that many variations can be introduced in saidpreferred embodiments without exceeding the object of the claimedinvention.

1. A method to evaporate active ingredients from a liquid solution, inwhich said liquid solution comprises a solvent and at least one type ofactive ingredient, the method comprising: dispensing in controlled timeperiods doses of said liquid solution on a liquid retaining support,wherein the solvent is evaporated from said support such that only theactive ingredient remains on the support, and wherein the activeingredient is evaporated from the support after most of the solvent hasevaporated.
 2. A method according to claim 1, wherein the time periodsbetween doses are controlled such that a dose of the liquid solution isdispensed on said support at an instant in time after the evaporation ofmost of the active ingredient of the previous dose from the support. 3.A method according to claim 1, wherein the time period between twoconsecutive doses is greater than the time necessary to evaporate thesolvent and the active ingredient from the support.
 4. A methodaccording to claim 3, wherein the time period between two consecutivedoses is substantially similar to the time necessary to evaporate thesolvent and the active ingredient from the support.
 5. A methodaccording to claim 1, wherein the time periods between doses arecontrolled by means of an electronic timer which is associated toelectromechanical means to allow dispensing a dose of liquid solutionafter the established time period between doses.
 6. A method accordingto claim 1, wherein a dose of liquid solution is dispensed by impulseactivation by the user.
 7. A method according to claim 1, wherein a doseof liquid solution is dispensed automatically in a pre-established timeinterval.
 8. A method according to claim 1, wherein the solvent and/orthe active ingredient are heated during their evaporation, at atemperature less than 100° C.
 9. A method according to claim 1, whereinthe solvent and the active ingredient are evaporated at room temperature10. A method according to claim 1, wherein an air stream is applied tothe solvent and/or to the active ingredient retained in the support. 11.A method according to claim 1, wherein the doses of liquid solution aredispensed from a liquid reservoir.
 12. A method according to claim 1,wherein the doses of liquid solution are dispensed in a coordinatedmanner in two different liquid retaining supports at different instantsin time, such that the active ingredient without solvent is alwaysavailable in at least one of said supports.
 13. A method according toclaim 1, wherein the active ingredient is an insecticide and/or aperfume.
 14. A method according to claim 1, wherein the doses of liquidsolution are dispensed by means of dripping.
 15. A method according toclaim 1, wherein the doses of liquid solution are dispensed by means ofa spray or an aerosol.
 16. A method according to claim 1, wherein thedoses of liquid solution are dispensed by means of breaking capsulescontaining the liquid solution.